. >>> a second victim has been identified, crystal campbell. in the last five minutes, we heard a graduate student in boston university is the third victim. still waiting for a name on that one. >> and an interfaith memorial service has been planned in boston for thursday. the white house says the president will attend. >>> tonight, boston's mayor says the city is strong. >> we are boston. we are one community and we will not let terror take us over. >> our bruce leshan is in boston tonight with more on the investigation. >> reporter: the investigation of what the boston police department calls its biggest, most complicated crime scene ever, continues to condense from 15 blocks to 12 blocks to now, about 10 blocks. but the search for the killers here continue to expand. and the fbi says someone, someone knows who did this. they ask people to think. somebody talk about targeting the boston marathon? did they hear explosions in a rural area? did they see anyone carrying a heavy black or dark colored backpack? >> we can asking anyone who may have